I have tried this with both RecordAudioActivity and RecordMessageActivity. Setting the PlayBeep property to True doesn't play the beep after the prompt. Is there something I am missing?
Found this post that solves the problem: http://gotspeech.net/forums/post/6083.aspx
However, now the Action prompts play to the end. I guess a sequence activity can solve this by having one activity to record the audio and following that a MenuActivity or QuestionAnswerActivity can ask the user to choose an action. The latter activity can have CanBargeIn = true.